The disclosure relates generally to X-ray equipment. More specifically, this application relates to C-arm spin acquisition trajectories of an X-ray machine, and more particularly to C-arm spin acquisition trajectories that enable 3D imaging of dynamic processes.
X-ray machines are known devices that allow individuals, such as healthcare practitioners, to capture images, in a relatively non-intrusive manner, of bones and other tissues, bone density, implanted devices, catheters, pins, and a wide variety of other objects and materials that are within a patient's body. In this regard, the term X-ray may refer to any suitable type of X-ray imaging, including film X-ray shadow grams and X-ray fluoroscopic imaging, which may refer to images that are produced by the conversion of an incident X-ray pattern to a “live” enhanced or intensified optical image that can be displayed on a video monitor, nearly contemporaneously with the irradiation of the portion of the patient's body that is being imaged.
Often, when a practitioner takes X-rays of a patient, it is desirable to take several X-rays of one or more portions of the patient's body from a number of different positions and angles, and preferably without needing to frequently reposition the patient. To meet this need, C-arm X-ray diagnostic equipment has been developed. The term C-arm generally refers to an X-ray imaging device having a rigid and/or articulating structural member having an X-ray source and an image detector assembly that are each located at an opposing end of the structural member so that the X-ray source and the image detector face each other. The structural member is typically “C” shaped and so is referred to as a C-arm. In this manner, X-rays emitted from the X-ray source can impinge on the image detector and provide an X-ray image of the object or objects that are placed between the X-ray source and the image detector.
In many cases, C-arms are connected to a movable support. In such cases, the C-arm can often be raised and lowered, be moved from side to side, and/or be rotated about one or more axes of rotation. Accordingly, such C-arms can be moved and reoriented to allow X-ray images to be taken from several different positions and angles and different portions of a patient, without requiring the patient to be repositioned.
When images are acquired from a number of different gantry angles (i.e., for different orientations of the C-arm with respect to the imaged region of interest), these images may be reconstructed into a volumetric representation of the structures of the object contained in the imaged region. Generally, such an acquisition is performed by using a so-called spin acquisition, i.e., by rotating the C-arm gantry by about 200-220 degrees around a rotational axis. This limitation of the angular range is a consequence of mechanical limitations of the gantry, which, in particular, does not allow for a continuous rotation along a single axis of rotation. However, this angular range also corresponds to the angular range required for (nearly) complete data (e.g., 180 degrees plus the fan angle), and high-quality 3D images may be reconstructed from the collected data. In situations where a sequence of 3D datasets is to be acquired, the spin acquisition may be repeated periodically (and the gantry moved back to the start position in-between spins), or a back-and-forth spin acquisition may be performed, where x-ray image data is acquired during both directions of motion of the gantry.
Current approaches for use of these C-arm devices consist of a sequence of back-and-forth spin acquisitions. Of particular interest is the use of this back-and forth spin using a C-arm in order to acquire data for dynamic 3D imaging, such as perfusion imaging. Specifically, the dynamic nature of the perfusion is accommodated by acquiring a number of consecutive spin datasets, where the delay between consecutive datasets is minimized by acquiring data both on the forward spin, and on the backward spin. However, a significant drawback of this method consists of the fact that there is still a dead-time of about 1.5 seconds between the end of the spin acquisition in one direction, and the start of the acquisition in the other direction. This delay is due mainly to mechanical reasons (allow gantry vibrations to settle). No data is collected during this dead-time, which is mostly due to the fact that the data is from a single, static gantry position, and thereby does not provide any 3D information.
Accordingly, a means for acquiring data along a trajectory whereby this dead-time is eliminated, thereby minimizing gantry vibration and enabling improved image quality as a result of increased data completeness, is desirable.